The present invention relates to an air-permeable cap to be mounted on a housing for automobile headlamp or the like for rendering the housing ventilative and rendering the interior of the housing waterproof and an outdoor lamp, automobile lamp and automobile electrical component comprising the air-permeable cap.
Heretofore, an air-permeable cap has been used for housing for automobile electrical components such as automobile headlamp, rear lamp, fog lamp, turn lamp, motor, various pressure sensors, pressure switches and ECU (electronic control unit) case and devices such as portable telephone, camera, electric razor, electric toothbrush and outdoor lamp.
In some detail, the foregoing device housing can be provided with the foregoing air-permeable cap at an opening formed therein for communicating between the interior and the exterior thereof to prevent the entrance of water, dust, etc. into the interior thereof, relax the change in the pressure in the device housing due to the temperature change, allow sound to be transmitted between the interior and the exterior of the device housing or allow the release of gas produced in the device housing.
As shown in FIG. 7, a device housing 50 such as automobile electrical component which is subject to exposure to contaminants such as rainwater, muddy water and oil can be provided with an air-permeable cap which may be in the form of L-shaped cylindrical body 51 or U-shaped cylindrical body (not shown) or provided with a maze structure thereinside as shown in FIG. 8, which fits on a mounting opening 50a formed at the neck portion of the housing for mounting the air-permeable cap. In this arrangement, the foregoing contaminants can be prevented from being directly applied to the mounting opening 50a. As a result, the foregoing mounting opening 50a cannot be clogged, assuring the air permeability and waterproofness of the mounting opening 50a. 
As shown in FIG. 9, in the case where further dustproofness or waterproofness is required, a filter member 54 may be stuck to the forward end of the mounting opening 50a formed at the neck portion of the device housing 50 with an annular double-coated tape 55 or the like before the foregoing cylindrical body 51 is fitted on the mounting opening 50a formed on the neck portion. In the case where the filter member 54 has an insufficient strength, the filter member 54 may be reinforced by a reinforcing material 53.
However, even if the foregoing cylindrical body 51 is fitted, water, dust or the like cannot be occasionally prevented from entering into the interior of the housing for devices such as automobile electrical component. When the length of the foregoing cylindrical body 51 is increased to make it more difficult for water, dust or the like to enter into the interior of the housing, it disadvantageously adds to the space required for the mounting of the cylindrical body 51 and the cost of the cylindrical body 51. Further, when the cylindrical body 51 is with a maze structure 52 thereinside, the cylindrical body 51 is disadvantageously complicated, adding to its cost. Moreover, when the foregoing filter member 54 is used, it is disadvantageous in that a step of mounting the filter member 54 or the like must be added before the step of fitting the cylindrical body 51.
On the other hand, the foregoing cylindrical body 51 can be easily fitted on the mounting opening 51 but can easily come off from the mounting opening 51. By increasing the thickness of the cylindrical body 51, the fitting force (pull strength) of the cylindrical body 51 with respect to the mounting opening 50a formed at the neck portion of the device housing 50 can be increased. However, when the thickness of the cylindrical body 51 is increased, it is disadvantageous in that the size of the cylindrical body 51 itself increases, adding to the space required for mounting and the cost of the cylindrical body 51.
Known besides the foregoing cylindrical body 51 is a vent filter member proposed in JP-A-10-85536 (The term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) (see FIG. 10). The vent filter member comprises a substantially closed-end cylindrical cover cap 61, a substantially cylindrical elastomer member 62 fitted in the cover cap 61 coaxially of the cover cap 61, an air passage formed between the inner wall of the cover cap 61 and the outer wall of the elastomer member 62 and between the bottom surface of the cover cap 61 and the lower end of the elastomer member 62, and a water-repellent membrane 64 covering an opening in the bottom of the elastomer member 62. The top opening of the elastomer member 62 forms a mounting portion 65 at which the vent filter member is fitted on the mounting opening 50a of the device housing 50.
Provided standing at the bottom surface of the cover cap 61 close to the inner wall of the cover cap are four fixing pins 66. Formed in the peripheral portion of the elastomer member 62 are pin holes 67 corresponding to the respective fixing pins 66. The fixing pins 66 of the cover cap 61 are inserted into the respective pin holes 67 of the elastomer member 62 in such an arrangement that the water-repellent membrane 64 is protected (the water-repellent membrane 64 and the bottom surface of the cover cap 61 are opposed to each other). The forward end of the fixing pins 66 protruding from the respective pin holes 67 are then thermally deformed. In this manner, the elastomer member 62 is positioned and fixed in the cover cap 61.
However, the vent filter member requires a complicated structure to fix the elastomer member 62 to the cover cap 61 and thus is so great in size that it can be hardly provided in a compact form and at a reduced cost. Further, in order to fixing the elastomer member 62 to the cover cap 61, it is necessary that the pin holes 67 of the elastomer member 62 be positioned at the respective fixing pins 66 of the cover cap 61, requiring much time to fix the elastomer member 62 to the cover cap 61.
It is therefore an object of the present invention to provide a compact and inexpensive air-permeable cap and an outdoor lamp, automobile lamp and automobile electrical component comprising such an air-permeable cap.
The foregoing object of the present invention will become apparent from the following detailed description and examples.
The foregoing object of the invention is accomplished with the first subject of the invention which lies in an air-permeable cap comprising a closed-end cylindrical cover member, a substantially cylindrical body fitted in the closed-end cylindrical cover member, and an air passage formed between the inner wall of the closed-end cylindrical cover member and the outer wall of the substantially cylindrical body and between the bottom surface of the closed-end cylindrical cover member and the lower end of the substantially cylindrical body, wherein the mounting portion at which the air-permeable cap is mounted on the mounting opening of the housing is formed at the top of the substantially cylindrical body. The second subject of the invention is an outdoor lamp comprising the foregoing air-permeable cap. The third subject of the invention is an automobile lamp comprising the foregoing air-permeable cap. The fourth subject of the invention is an automobile electrical component comprising the foregoing air-permeable cap.
More specifically, the foregoing object of the invention can be attained by the following means.
(1) An air-permeable cap comprising a closed-end cylindrical cover member, a substantially cylindrical body fitted in said closed-end cylindrical cover member, and an air passage formed between the inner wall of said closed-end cylindrical cover member and the outer wall of said substantially cylindrical body and between the bottom surface of said closed-end cylindrical cover member and the lower end of said substantially cylindrical body, wherein the mounting portion at which the air-permeable cap is mounted on the mounting opening of the housing is formed at the top of said substantially cylindrical body.
(2) The air-permeable cap as described in (1) above, wherein a plurality of protrusions are formed at a predetermined interval along the periphery of said substantially cylindrical body, said protrusions come in contact with the inner wall of said closed-end cylindrical cover member so that said cylindrical body is positioned and fixed and an air passage is formed between said protrusions.
(3) The air-permeable cap as described in (1) or (2) above, wherein the elastic modulus of said cover member is different from that of said substantially cylindrical body.
(4) The air-permeable cap as described in any one of (1) to (3) above, wherein said cover member and said substantially cylindrical body are fitted at two or more contact portions.
(5) The air-permeable cap as described in any one of (1) to (4) above, wherein the air permeation sectional area of said air passage is 1xc3x9710xe2x88x926 m2 or more at all positions.
(6) The air-permeable cap as described in any one of (1) to (5) above, wherein the top opening of said cover member or the bottom opening of said substantially cylindrical body is covered by a filter member.
(7) The air-permeable cap as described in (6), wherein the air permeation sectional area of said filter member is 3xc3x9710xe2x88x926 m2 or more.
(8) The air-permeable cap as described in (6) or (7) above, wherein said filter member is a porous membrane made of polytetrafluoroethylene.
(9) The air-permeable cap as described in any one of (6) to (8) above, wherein said filter member is rendered oil-repellent.
(10) An outdoor lamp comprising an air-permeable cap as described in any one of (1) to (9) above.
(11) An automobile lamp comprising an air-permeable cap as described in any one of (1) to (9) above.
(12) An automobile electrical component comprising an air-permeable cap as described in any one of (1) to (9) above.
The air-permeable cap of the invention comprises a substantially cylindrical body fitted in a closed-end cylindrical cover member and thus requires only a simple structure to fix the cover member and the substantially cylindrical body to each other. Accordingly, an air-permeable cap can be easily provided in a compact form and at a low cost.
Further, the outdoor lamp, automobile lamp and automobile electrical component according to the invention comprise the foregoing air-permeable cap and thus require only a reduced space to mount the air-permeable cap.